Damping device

ABSTRACT

A damping device, in particular for damping or preventing pressure impacts, like pulsations, in hydraulic supply circuits, comprising a damping housing ( 1 ) which surrounds a damping chamber and has at least one fluid inlet ( 13 ) and a fluid outlet ( 15 ) and a damping tube ( 21; 51 ) located in the flow path between the damping inlet and outlet, said damping tube having at least one branch opening ( 29; 73, 75, 77, 79, 81 ) passing through the tube wall and leading to a Helmholtz volume ( 27; 53, 55, 57, 59, 61 ) inside of the damping housing ( 1 ) for forming a Helmholtz resonator in a region positioned inside of the length of the damping tube, characterized in that a fluid filter ( 35 ) is arranged inside of the damping housing ( 1 ) in the flow path running between the fluid inlet ( 13 ) and fluid outlet ( 15 ).

The invention relates to a damping device, in particular for damping or preventing pressure impacts, such as pulsations, in hydraulic supply circuits, comprising a damping housing which surrounds a damping chamber and has at least one fluid inlet and a fluid outlet and a damping tube located in the flow path between the fluid inlet and fluid outlet, said damping tube having at least one branch opening passing through the tube wall and leading to a Helmholtz volume inside of the damping housing in order to form a Helmholtz resonator in a region positioned inside of the length of the damping tube.

Damping devices of this type are state of the art. Such hydraulic dampers, which are also known as sound dampers or silencers, serve to reduce vibrations produced by pressure pulsations, which are periodically applied to a corresponding hydraulic system, in particular as a result of the operation of hydraulic pumps. As is disclosed in document DE 102 17 080 C1, the known damping devices of this type have a damping housing in the form of a circular cylinder, which is rounded in a spherical manner for example at both axial end regions, with the fluid inlet and the fluid outlet being located coaxial to the cylinder axis on a respective end region. For the reduction of noise which is created by vibrations produced by pressure pulsations, which reduction is realized by means of a Helmholtz resonator, the damping housing is radially expanded at least in regions relative to the damping tube determining the flow direction, so that a space containing a Helmholtz volume is formed, which the damping tube is connected to via the at least one branch opening.

On the basis of this prior art, the invention addresses the problem of providing a damping device of the afore-mentioned type, which can be particularly easily and advantageously integrated into existing hydraulic systems.

According to the invention, this problem is solved by means of a damping device having the features of Claim 1 in its entirety.

Accordingly, a significant distinctive feature of the invention is that a fluid filter is arranged inside of the damping housing in the flow path running between the fluid inlet and the fluid outlet. This design dispenses with a separate filter device which is normally essential in hydraulic systems for reasons of operational reliability. The integration of the fluid filter into the damping housing permits a particularly compact construction and, at the same time, an increase in operational reliability due to the absence of connecting tubing between the filter and the damper, with a reduction in the overall constructed space being achievable at the same time, so that the damping device can be used without difficulty even when the available installation space is limited. The damping device according to the invention is thus suitable even for mobile applications with particularly constricted space, for example, in hydraulic systems of aircraft or land vehicles.

In particularly advantageous exemplary embodiments, a fluid filter with a circular cylindrical filter element is provided, which is arranged in the damping tube with a cylinder axis coaxial to said damping tube. This makes it possible to realize a particularly compact construction, with the filter element simultaneously making it possible to achieve an intensification of the damping effect.

In particularly advantageous exemplary embodiments, the damping housing is formed circular cylindrical and is closed at both ends by means of a housing cover comprising one of the fluid inlet or the fluid outlet, on which the ends of the damping tube which extends coaxial to the cylinder axis are mounted, which damping tube is in a fluidic connection at its one end with the fluid inlet or fluid outlet of the corresponding housing cover, with the fluid inlet or fluid outlet of the respective other housing cover being connected to the inside of the damping tube via the filter element.

The arrangement can particularly advantageously be such that the filter element is mounted on the housing cover comprising the fluid outlet in such a way that the fluid outlet is connected to the internal filter cavity, which is surrounded by a circular cylindrical filter medium, the outer side of which adjoins the interior of the damping tube. During operation, the filter element can thus be flowed through from the outer side of the filter medium inwards so that, in a manner which is advantageous for the stability of the filter medium, the dynamic pressure existing during operation acts on said filter medium from the outside to the inside and can be absorbed for example via an internal support tube of the filter element.

In particularly advantageous exemplary embodiments, for the purpose of forming a plurality of Helmholtz resonators, the space between the outer side of the damping tube and the inner side of the damping housing is divided into several separate chambers, each of which is connected via at least one branch opening in the wall of the damping tube to the interior thereof. This allows the damping device to be set in a targeted manner to the damping of various frequencies. This is advantageous in particular in the case of variable-speed drives encountered in the hydraulic system, which drives generate a broad frequency range as the excitation spectrum of vibrations.

For a targeted tuning, chambers of different volumes can be provided and/or branch openings with different opening cross sections can be provided.

In this regard, the arrangement can particularly advantageously be such that, in the flow direction coming from the fluid inlet, successive chambers each have decreasing volumes. This makes it possible to realize resonators, which are successively tuned to lower and then increasingly higher base frequencies. In the flow direction coming from the fluid inlet, the branch openings of successive chambers are preferably each provided with increasing opening cross sections.

For different chamber volumes, it is possible for chambers which are located on a constant external diameter of the damping tube to have different axial lengths. Alternatively, the damping tube can have a stepped external diameter, so that chambers of different radial extension are formed and, for the purpose of a tuning to low frequencies, the damping tube is preferably able to abut the housing cover comprising the fluid inlet by means of a length section of reduced diameter.

The invention is explained in detail below based on exemplary embodiments depicted in the drawings, in which:

FIG. 1 shows a perspective oblique view, shown cut open in a central longitudinal plane, of an exemplary embodiment of the damping device according to the invention, depicted with approximately half the size of a functional embodiment, and

FIG. 2 shows a depiction, corresponding to FIG. 1, of a second exemplary embodiment.

With reference to the attached drawings, the invention is described in detail based on the example of a so-called silencer, which functions according to the principle of a Helmholtz resonator. The exemplary embodiment depicted in FIG. 1 has a damping housing 1 in the form of a circular cylindrical tubular body, which is provided in its two end regions 3 and 5 with an internal thread 7 or 9. A housing cover 11 is screwed to this internal thread at the end region 3 lying on the left in the drawings, in which housing cover a central passage forms a fluid inlet 13 for the supply of a respective fluid with applied pressure pulsations. A housing cover 14 is screwed to the internal thread 9 on the opposite end region 5, which housing cover, like the other housing cover 11, has a central passage as a fluid outlet 15. Both covers 11 and 14 are similarly formed as cylindrical threaded plugs and are secured by means of a locking pin 17 in the screwed-in state. For the purpose of sealing relative to the damping housing 1, a sealing ring 19 is arranged on the inner end of each cover 11, 14. In the screwed-in state, the outer ends of the cover 11, 14 are substantially flush with the tube ends of the damping housing 1.

In the exemplary embodiment depicted in FIG. 1, a circular cylindrical round damping tube 21 having a constant diameter over its entire length extends coaxial to the axis of the damping housing 1 between the housing covers 11 and 14. Both housing covers 11 and 14 have, on the inner sides which face one another, an axially projecting peripheral edge 23, on the outer side of which the sealing ring 19 for the sealing on the damping housing 1 is located. The facing end of the damping tube 21 abuts the inner side of the respective peripheral edge 23, with a sealing ring 25 forming the seal. Depending on the radial thickness of the peripheral edges 23, the damping tube 21 is thus kept at a distance from the inner wall of the damping housing 1, by which means a chamber 27 is created between the outer side of the damping tube 21 and the inner side of the damping housing 1, which chamber forms a Helmholtz volume. For the connection between the interior of the damping tube 21 and the chamber 27, in the tube wall of the damping tube 21 a branch opening 29 is formed in the vicinity of the inlet-side housing cover 11 and a branch opening 31 is formed in the vicinity of the outlet-side housing cover 14. In order to obtain a desired frequency tuning of the thus formed Helmholtz resonator, the branch opening 29 lying on the left-hand side is provided with a larger opening cross section than the other branch opening 31.

The outlet-side housing cover 14 has an axially recessed annular groove 33 which is offset from the peripheral edge 23 radially towards the inside, which forms the support for a filter element 35 which extends with a circular cylindrical shape coaxial to the cylinder axis on the inside of the damping tube 21 over more than half of the length of said damping tube. The filter element 35 has a hollow cylindrical filter medium 37 which surrounds an inner perforated support tube 39. As is standard in such filter elements, an end cap 41 is provided on the end of the filter element 35 which is on the left-hand side in the drawings, which end cap forms a mounting for the support tube 39 and the filter medium 37. The internal filter cavity 43 located inside the support tube 39 merges directly into the fluid outlet 15 at the outlet-side housing cover 14. In this arrangement, the filter element 35 forms a part of the flow path for the fluid flowing in via the fluid inlet 13 and flowing out via the fluid outlet 15, with said fluid flowing through the filter medium 37 from the outside to the filter cavity 43 which forms the clean side, from where the fluid exits via the immediately adjacent fluid outlet 15. During this process, the Helmholtz resonator formed by the branch openings 29 and 31 and the chamber 27 produces a noise damping, which is enhanced by the presence of the filter element 35 located on the inside of the damping tube 21.

The exemplary embodiment of FIG. 2 corresponds to the example of FIG. 1, apart from the fact that, instead of a damping tube with the same diameter throughout, a damping tube 51 with a stepped diameter is provided and that furthermore the space surrounding the stepped damping tube 51 is divided into several separate chambers 53, 55, 57, 59 and 61 which each form a Helmholtz volume. The damping tube 51 is stepped in such a way that its first length section 63 abutting the inlet-side housing cover 11 has a reduced diameter, while over the remaining part of its length extending to the outlet-side housing cover 14 the damping tube 51 has a constant diameter, which corresponds to the diameter of the damping tube 21 of FIG. 1. As FIG. 2 shows, the inlet-side first chamber 53 thus has a greater radial thickness than the other chambers 55, 57, 59 and 61. In the axial direction, the inner end of the first chamber 53 is delimited by an annular disc 65, which at the same time forms the one boundary of the following chamber 55. Additional annular discs 67 each form boundaries for the subsequent chambers 55, 57, 59 and 61. For each of the chambers, a branch opening is provided passing through the wall of the damping tube 51, which branch openings are identified from left to right in FIG. 2 with the reference numerals 73, 75, 77, 79 and 81. For targeted tuning of the damping device to desired frequency ranges, both the volumes and the shape of the chambers, which form the Helmholtz volumes for several Helmholtz resonators, are different. As mentioned above, the inlet-side chamber 53 has a greater radial thickness than the following chambers, which each have the same thickness in this respect, however, the axial length of the first chamber 53 is less than that of the second chamber 55. The axial lengths of the additional chambers 55, 57, 59 and 61 each decrease in the direction of the outlet-side housing cover 14. By contrast, the opening cross sections of the branch openings 73, 75, 77, 79, 81 increase the smaller the volume of the associated chamber. This arrangement results in a tuning to lower tones for the inlet-side first chamber 53, while the subsequent chambers 55, 57, 59, 61 are each tuned to higher tone frequencies. In conjunction with the additional noise damping by means of the installed filter element 35 it is thus possible to achieve a highly efficient damping.

For the fastening of the damping device to corresponding third components, four threaded holes 85 for fastening means and connection means are provided on the inlet-side housing cover 11 in an arrangement symmetrical to the fluid inlet 13. On the outlet-side housing cover 14 four threaded bolts 87 are provided in a corresponding arrangement relative to the fluid outlet 15. As the figures show, the filter element 35 is connected only to the outlet-side housing cover 14, so that a filter change requires only the removal of a housing cover, without having to take the whole damping device out of the system, as blocking of the inflow to the fluid inlet 13 is sufficient. 

1. A damping device, in particular for damping or preventing pressure impacts, such as pulsations, in hydraulic supply circuits, comprising a damping housing (1) which surrounds a damping chamber and has at least one fluid inlet (13) and a fluid outlet (15) and a damping tube (21; 51) located in the flow path between the fluid inlet (13) and fluid outlet (15), said damping tube having at least one branch opening (29; 73, 75, 77, 79, 81) passing through the tube wall and leading to a Helmholtz volume (27; 53, 55, 57, 59, 61) inside of the damping housing (1) in order to form a Helmholtz resonator in a region positioned inside of the length of the damping tube, characterized in that a fluid filter (35) is arranged inside of the damping housing (1) in the flow path running between the fluid inlet (13) and the fluid outlet (15).
 2. The damping device according to claim 1, characterized in that the fluid filter has a circular cylindrical filter element (35) which, with a cylinder axis coaxial to the damping tube (21; 51), is arranged in said damping tube.
 3. The damping device according to claim 1 or 2, characterized in that the damping housing (1) is formed circular cylindrical and is closed at both ends by means of a housing cover (11, 14) comprising one of the fluid inlet (13) or the fluid outlet (15), on which the ends of the damping tube (21; 51) which extends coaxial to the cylinder axis are mounted, which damping tube is in a fluidic connection at its one end with the fluid inlet (13) or fluid outlet (15) of the corresponding housing cover (11, 14), and in that the fluid inlet (13) or fluid outlet (15) of the respective other housing cover (11, 14) is connected to the inside of the damping tube (21; 51) via the filter element (35).
 4. The damping device according to claim 1, characterized in that the filter element (35) is mounted on the housing cover (14) comprising the fluid outlet (15) in such a way that the fluid outlet (15) is connected to the internal filter cavity (43), which is surrounded by a hollow cylindrical filter medium (37), the outer side of which adjoins the interior of the damping tube (21; 51).
 5. The damping device according to claim 1, characterized in that, for the purpose of forming a plurality of Helmholtz resonators, the space between the outer side of the damping tube (51) and the inner side of the damping housing (1) is divided into several separate chambers (53, 55, 57, 59, 61), each of which is connected via at least one branch opening (73, 75, 77, 79, 81) in the wall of the damping tube (51) to the interior thereof.
 6. The damping device according to claim 1, characterized in that chambers (53, 55, 57, 59, 61) of different volumes are provided.
 7. The damping device according to claim 1, characterized in that branch openings (73, 75, 77, 79, 81) with different opening cross sections are provided.
 8. The damping device according to claim 1, characterized in that, in the flow direction coming from the fluid inlet (13), successive chambers (53, 55, 57, 59, 61) each have decreasing volumes.
 9. The damping device according to claim 1, characterized in that, in the flow direction coming from the fluid inlet (13), the branch openings (73, 75, 77, 79, 81) of successive chambers (53, 55, 57, 59, 61) each have increasing opening cross sections.
 10. The damping device according to claim 1, characterized in that the damping tube (51) has a stepped external diameter and abuts the housing cover (11) comprising the fluid inlet (13) by means of a length section (63) of reduced diameter. 